The dry-type transformer is a huge component. There are many gaps in it. Generally, voltage and current can be transmitted between the gaps. If you are not careful, you will get an electric shock. The gap of the dry-type transformer is also necessary. To protect, otherwise it is easy to malfunction.

Gap protection means that the two poles of the circuit are generally composed of angular bars. One pole is fixed on the dry-type transformer insulator to connect a live wire, and the other pole is grounded. After the gap breaks down, the arc rises and stretches between the angular bars. The arc can be extinguished by itself. The disadvantage of the gap protection technology is that it cannot extinguish the arc by itself when the arc current is more than tens of amperes. When the lightning overvoltage occurs, the single-phase, two-phase or three-phase gap may break down and cause grounding. Fault, two-phase or three-phase short-circuit fault, so that the line power circuit breaker protection action opens.

In the early stages of development and use of electric power devices, most of the power transmission is through bare conductor overhead lines. The overhead conductors are generally 6 to 18 meters above the ground. The lightning overvoltage generated by the lightning intrusion wave causes the insulation breakdown of the line or equipment and damages it. At that time, people artificially created insulation weaknesses or gap devices on lines or equipment. The breakdown voltage of the gap was lower than the lightning impulse insulation level of the line or equipment. The gap was in a state of isolation and insulation under normal operating voltage, and it was strong when lightning occurred. The overvoltage causes the gap to break down, resulting in grounding protection, which protects the insulation of the line or equipment.